Psilacrum lineatum Riccardi & Ismay, 2017

Ismay, John Waland, 2017, First record of Psilacrum Becker 1912 (Chloropidae, Diptera) from Brazil, with the description of a new species, Zootaxa 4329 (5), pp. 497-500 : 497-500

Psilacrum lineatum Riccardi & Ismay sp. nov. ( Figs. 1–7 )

Examined material: Holotype : 1 ♂ Brazil, Rio Grande do Sul, Camaquã, Pacheca, Rio Camaquã ; 17–25.xi.2011; S31.12159 W31.79237; Malaise ; F.D. Kirst & R.F. Krüger col [abdomen and wing prepared, MZUSP]. Paratypes (6 specimens) : 1 ♀ same data as holotype [figures 1–2, MZUSP] ; 2 ♀ Brazil, Rio Grande do Sul, Arroio Pelotas, Mata da Galatéia , S31.67327 W52.21666, 27.x–4.xi.2011, Malaise, F.D. Kirst & R.F. Krüger col. [1 ♀ abdomen prepared, MZUSP] ; 1 ♀ Brazil, Rio Grande do Sul, Arroio Corrientes, Fazenda Corrientes , S31.55222 W52.13759, 5.xi.2011, Malaise, F.D. Kirst & R.F. Krüger col. [ OUMNH] ; 1 ♀ Brazil, Rio Grande do Sul, Arroio Corrientes, Fazenda Corrientes , S31.55506 W52.14336, 28.x–5.xi.2011, Malaise, F.D. Kirst & R.F. Krüger col. [ DZUP] ; 1 ♀ Brazil, Rio Grande do Sul, Barra do Ribeiro, RPPN Barba Negra, Mata da Faxina , S30.38214 W51.11699, 19–27.xi.2011, Malaise, Kirst & R.F. Krüger col. [ MZUSP].

Description. Body length, 2.2–2.55 mm. Wing length, 1.95–2.25 mm. Diagnosis. Almost entirely yellow species with black scutal markings and partially darkened middle and posterior legs.

Head (figs 1–2). Broader than deep and deeper than long (0.83: 0.65: 0.46 mm), entirely yellow except for black ocellar tubercle. Head and thoracic setae black. Ocellar setae displaced, but on paratypes long, proclinate and divergent, equal to inner vertical seta. About seven orbital setae developed, decreasing in size anteriorly, the most posterior equal in length to width of ocellar tubercle. Outer vertical seta strongly developed, slightly longer than half maximum width of frons; inner vertical seta circa three quarter length of outer vertical seta; a further seta anterior to inner vertical seta placed outside lateral margin of ocellar triangle. Frons slightly broader than long (0.44: 0.37 mm), breadth measured at level of anterior ocellus, lateral margins of anterior margin of frons very slightly concave, slightly narrowed anteriorly, front margin very slightly concave, yellow with many brown setulae, one crossed pair of setulae at anterior margin much longer than remainder, undusted but microstriate. Ocellar triangle bare, small, extending to half length of frons, posteriorly one third width of frons, lateral margins straight, shining, yellow; postocellar setae in holotype slightly distorted, but in paratype convergent and upright, outer vertical seta upright and directed slightly laterally, inner vertical seta incurved and upright. Eye oval, long axis slightly oblique with short, sparse pubescence. Face as broad as deep, strongly concave; a faint narrow carina between antennae, absent below level of eye; antennae yellow, first flagellomere reniform, deeper than long; arista basally black, with strong short pubescence (equal in length to basal diameter of arista), 4 times as long as first flagellomere; gena narrow, slightly narrower than length of first flagellomere, yellow with whitish dusting, one row of brown setulae on ventral margin, one setula each longer at anterior and posterior margins; occiput yellow, with faint brown lines at level of posterior corner of ocellar triangle and small setulae along eye margin; proboscis yellow, short with white setulae, poorly sclerotized; palpus yellow, small, equal in length to antenna, slightly curved upwards, with brown setulae; mouth edge not protruding; clypeus yellow. Thorax (figs. 1–2). Scutum about as long as broad (0.83: 0.80 mm), yellow, darker orange yellow on central stripe, the latter occupying entire space between dorsocentral lines, and on two patches, the latter triangle shaped pointing posteriorly, lateral to dorsocentral lines, anterior and posterior to transverse suture; all markings ceasing well anterior to scutellum, leaving a broad yellow band (as long as antenna is wide); central stripe with black median line (occupying one third width); lateral patches with black rounded triangular mark on posterior half, dorsal to wing base; scutum entirely shining with sparse pale setulae; one posterior dorsocentral seta developed, slightly longer than outer vertical seta, no acrostical seta developed; postpronotal lobe yellow with long seta equal to inner vertical; notopleuron with 1 plus 1 setae; anterior post-alar as long as outer vertical seta. Pleura yellow, entirely shining; a few setulae on dorsal margin of katepisternum. Scutellum yellow, shining, slightly broader than long (0.44: 0.37 mm), shield-shaped with few black setulae on lateral margin, disc bare; apical scutellar seta with separation equal to that of posterior ocelli; one pair of lateral setae developed at two third length of scutellum; apical pair as long as scutellum; lateral seta two thirds length of apical scutellar seta; apical and lateral setae on small black tubercles; post-scutellum orange yellow, shining. Halter pale yellow. Wing (fig. 3). Translucent with brown veins covered in sparse brown microtrichia; costal ratios measured from basicosta to point where R1 touches costa, then R2+3, then R4+5: 0.98: 0.96: 0.41: 0.26 mm; cell r1 narrower than cell r2+3, veins R4+5 and M1+2 almost parallel up to costal wing margin, where they diverge very slightly. Legs (fig. 1). Mainly yellow, shining; posterior tibia yellow at extreme base, black on remainder; posterior tarsus yellow on basal two segments, black on apical three segments; apical tarsal segment scarcely wider than basal segment; posterior tibial organ well developed, occupying slightly more than middle third of tibia and slightly more than half width of tibia, more than five times as long as wide; setulae on coxae, trochanters and basis of femur almost white; setulae on remainder of legs black. Abdomen. Yellow, shining with black setulae; centers of tergites 1+2, 3 and 4 with a light brown patch and a darker spot at lateral margin; underside pale yellow. Male terminalia (figs. 6–7). Epandrium broader than deep, surstylus incurved, short, not meeting in mid-line, inner apex with a complex of serrations and setae; cercus small, as broad as long, separated by a space equal in width to each cercus with longer apical seta and several longer more basal setae. Hypandrium open, with inner arm very long and outer arm very short; basiphallus oval; distiphallus short and membranous; postgonite short, with several short setae and partially fused to pregonite. Female terminalia (figs. 4–5). Tergites 6–8 narrow, about twice as long as broad; sternite 7 with a semicircular brown spot; cercus brown, long and narrow.

Etymology. The species name lineatum (of a line) is derived from Latin, referring to the stripe in the middle of the scutum.

Comments. We have seen two females from Rio Grande, which have a different color-pattern on the scutum, and are therefore excluded from the type series. The black central stripe is lacking and the pair of lateral spots is very long. Males are needed to confirm their identity.

Figures

FIGURES 1 – 3. Psilacrum lineatum. 1, habitus (PT). 2, dorsal view (PT). 3, wing (HT). Scale bar 1 mm.

FIGURES 4 – 7. Psilacrum lineatum abdomen (PT). 4, tergite 8 and cerci in dorsal view. 5, sternite 8 and cerci in ventral view. Scale bar 0.1 mm. FIGURES 6 – 7. Psilacrum lineatum male terminalia (HT). 6, epandrium in terminal view. 7, illustration of the male terminalia in ventral view. Scale bar 0.1 mm. Abbreviations: bas, basiphallus; cer, cercus; dis, distiphallus; ep, epandrium; hyp, hypandrium; phal, phallapodeme; pog, postgonite; prg, pregonite; sur, surstylus.